Im building a new ICF home and having some concerns on Knee walls. First the house will have a full ICF basement with a 2' over dig or thereabouts. Im also using ICF for the knee wall for the stick built garage and the front porch. However with the over dig of the basement there is a empty space between the basement walls and where the ICF knee wall will be as well as the Knee wall footing. How do I bridge this space when using ICF? What are my options on this? Im just having a hard time getting my mind around it. Ive seen the block lintels used when a block foundation and Ive searched the internet for ideas but either Im dense (which is likely) but just cant find anything.

It's probably because of my lack of construction experience, but I'm having a hard time visualizing what you want to accomplish. I've only known knee walls in the context of upstairs walls against the roof, or maybe a porch wall. Can you post a sketch? What is the overriding reason for using a knee wall in the basement?

I would post a sketch if I knew how....lol I'm calling it a knee wall but its just the foundation wall for the garage and the another for the front porch. I only need the footer of the garage below the frost line so it doesn't go down to the basement footer. I will have a footer for the garage and then I'm using ICF to form up above grade then build my garage on top. The garage will be a side load so to will connect to the house. I don't know if this makes any more sense or not. The big problem is having a footer for the garage connect to the house when the ground under the footer location is missing for 2' from the over dig.

Makes sense now. I guess I didn't have that problem since I have just a crawl space under the house and the footer for the adjoining garage wall was at the same depth. I don't know how to address that other than place basement wall concrete first, then back fill and compact, and then do the garage footer, but maybe there's a better way.

Keep the garage footer on undisturbed ground by stepping it up to garage level just like you would with concrete block construction.  Make the steps multiples of the ICF block.  No worry about loose earth under the footer this way.

Here's what my brother said. He spent several years installing manufactured homes on permanent foundations, many of them over basements.

Well first you don't excavate the basement and the garage at the same depth. When you pour the garage or later you can drill in connecting rebar between the wall of the garage foundation and the wall of the basement.

If your basement excavation isn't more than about 4' deeper than the garage I would go along with Alton's suggestion. Otherwise, putting the garage in after the basement is in looks like probably the way to go. You could stab rebar through the foam of the basement wall to tie into the garage foundation wall. I don't think it would be overly critical to not have the garage footer and foundation wall poured continuous with the basement footer and wall as long as you have good rebar connection between them and very well compacted soil under the garage footer.

I think what you are looking for is what I have been calling a pilaster.

Anyway, when I formed my basement footings, I extended the footings out to the edge of the over dig where my front porch and garage footings intersected with the ICF wall.  I installed rebar dowels in these footing extensions just like the rest of the footing.  Then after the ICF basement wall was poured and waterproofed, I had a block layer lay 8"x16" CMU on this footing extension up to the height of where my porch and garage footings would be.  Then when it came time to dig the porch and garage footings, I attached my footing form boards to the these block pilasters with tap cons, i.e. blue screws.  I also drilled holes through the block so that I could run rebar from the pilaster into the footings.  Then when we poured the footings we also filled the block pilasters full of concrete as well.  See photo below.

Another thing I did where I had a porch slab and garage slab butt up against the ICF basement wall was to insert rebar dowels through the outer portion of ICF every 16" at roughly the middle of the slab height prior to the ICF pour.  These dowels extended ~24" into the slabs.  I also had the block layer build 8"x16" block columns approximately 4' on center resting on the footing and against the ICF wall.  These were then filled with concrete during the slab pour and provide assurance that the slab will not settle any next to the ICF wall.   In the photo below you can see my porch slab base on the right which was ~8" higher than the garage slab base on the left.  This photo is where the two intersected.

bridge it. Very simple with ICf. screw a piece of 2x to the face of the footer for the garage (down 1 1/2" from the top of the footer) and to the ICF wall for the basement. Use a 2x12 and place it on the 2x you installed to "continue" the footer across the gap forming a bridge. If your block brand has a T corner, use that to build the corner of your basement where it would intersect the garage stem wall. Continue the garage stem wall over the 2x12 platform and intersect with your T block in your basement. Use standard corner block below obviously. Install #5s about every course horizontally and extend them about 2' into the basement wall and garage stem wall. You are basically constructing a cast in place concrete beam. Pour the wall and stem wall, then remove the 2x12 under it if you want or leave it there and burry it. Much easier and faster than stepping a footing. Most residential applications loads are so low, especailly in this area, a 3 or 4' tall concrete beam spanning a few feet is extremely adequate.
Run it by your local inspector however, they may want you to step it. Bridging is the common way around here.

Thanks for all the input. I spoke with my inspector and he informed me the beam idea would pass for him. I'll probably go this route as it seems way less labor intensive. Thanks again everyone for your help..

Just for reference, the Canadian Codes do not allow bridging. The footing must be step as Alton mentioned with the rise not exceeding 24". so if there is more height you make more step. As mentioned you can step 18" to meet the Nudura form height.

If you garage slab is to run into the side wall of the basement later, it often works well to insert a brick ledger at that point to carry the floor later.

bridge, around here (Iowa) is allowed depending on the inspector or area for residential. So even some places, they do not allow it. What is interesting is its really no different than a very short grade beam, or even a an elevator floor (such as crawl space) on piers, so not sure why its not allowed everywhere if the engineering is there to back it up.

However on our commercial design we always step the footings as mentioned.

Not sure if you are planning on doing any of this work yourself or contracting it all out, but the block pilaster that I mentioned above to span across the over dig area can be done pretty easily DIY. It doesn't have to be pretty, it just has to hold the concrete in place when you pour the footing. If you stack the blocks in alternating courses, you can glue them together with construction glue such as Loctite PL Premium or get a bag of surface bonding cement and bond them externally with just a trowel applied mixture of cement. Then when you backfill, everything is pretty much locked in place. The poured concrete during the footing pour then makes it a monolithic structure. The same can be done with the slab support block columns adjacent to the basement wall.